Vieng Xai weather in September

In September, Vieng Xai sees average daytime highs of 27°C and overnight lows near 20°C, with 193 mm of rain across 20.1 wet days and about 12.1 hours of daylight. It is the 6th-warmest and 5th-wettest month of the year here.

Day-to-day highs hold fairly steady near 27°C through the month. The sky is clear or mostly clear about 12% of the time in September, and the air most often feels muggy.

Daylight stretches from about 12 h 24 min at the start of September to 11 h 48 min by month's end. Set against the rest of the year, September is Vieng Xai's 8th-clearest and 12th-windiest month. For the whole year in context, see Vieng Xai's year-round climate.

Daytime high
27°
6th warmest
Overnight low
20°
8th coldest
Rainfall
193 mm
20.1 wet days
Daylight
12 h 06 min
5:54 AM – 6:01 PM
Cloud cover
77%
8th clearest
Wind
4 km/h
12th windiest
Solar energy
4.25 kWh/m²
Travel score
4.7
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 27°C through the month.

A typical September day in Vieng Xai reaches about 27°C in the afternoon and slips back to 20°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 23°C and 30°C. Set against its neighbours, September runs about 1°C cooler than August and about 2°C warmer than October.

15°20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
12821
22821
32821
42821
52821
62821
72721
82720
92720
102720
112720
122720
132720
142720
152720
162720
172720
182720
192720
202720
212720
222720
232720
242719
252719
262719
272719
282719
292619
302619

How September really feels in Vieng Xai

Once humidity and wind are folded in, September averages 0 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Vieng Xai weather by month

How September compares with the rest of the year at a glance. September is the 6th-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan20° / 11°224.410.97.0
Feb22° / 12°143.811.37.6
Mar25° / 15°6010.611.96.8
Apr28° / 18°10917.712.55.1
May29° / 20°20523.2133.7
Jun29° / 22°20124.213.23.2
Jul29° / 22°26426.213.13.3
Aug28° / 21°30226.812.73.6
Sep27° / 20°19320.112.14.7
Oct25° / 18°9114.211.56.1
Nov23° / 15°326.3117.3
Dec20° / 11°194.210.87.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 12% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 13% of September, with mostly cloudy or overcast conditions the remaining 75%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
11783
21684
31684
41684
51783
61882
71882
81882
91882
102179
112179
122179
132278
142377
152476
162575
172674
182674
192773
203070
213070
223169
233268
243367
253466
263466
273565
283565
293565
303763

Chance of precipitation in September

Any precipitation

Vieng Xai gets around 193 mm of rain over 20.1 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 68% and peaks near 80% on the wettest days. The odds ease toward the end of the month.

0%20%40%60%80%151015202530
Rain chance (%)
180
280
379
479
578
677
777
876
975
1074
1174
1273
1372
1470
1569
1668
1766
1865
1964
2063
2161
2260
2359
2458
2557
2657
2756
2856
2955
3055

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels muggy — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the muggy band about 59% of days. Sticky, muggy-or-worse air turns up on roughly 87% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
10015049
20015148
30015247
40125245
50125443
60135442
70135640
80145738
90145936
100255835
110256033
120266131
130366130
140376228
150386326
160396325
1704106224
1804116223
1904126222
2005136121
2105146120
2205156119
2305166118
2406166117
2506176116
2607186015
2707196014
2807206013
2907206112
3018215911

Wind in September

Winds average 4 km/h in September, the calmest month.

Across September, daily wind ranges from about 4 km/h on the calmest days to 5 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (km/h)Feels
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
255calm
265calm
275calm
285calm
295calm
305calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 24 min at the start of September to 11 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 36 minutes over September. Sunrise moves from 5:51 AM to 5:57 AM, and sunset from 6:15 PM to 5:47 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.45:516:15
212.45:516:14
312.45:516:13
412.45:516:12
512.35:516:11
612.35:526:10
712.35:526:10
812.35:526:09
912.35:526:08
1012.25:536:07
1112.25:536:06
1212.25:536:05
1312.25:536:04
1412.25:546:03
1512.15:546:02
1612.15:546:01
1712.15:546:00
1812.15:545:59
1912.15:555:58
2012.05:555:57
2112.05:555:56
2212.05:555:55
2312.05:565:54
2412.05:565:53
2511.95:565:52
2611.95:565:51
2711.95:575:50
2811.95:575:49
2911.95:575:48
3011.85:575:47

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.25 kWh/m².

For context, solar energy here swings from a low near 3.16 kWh/m² to a high of 5.2 kWh/m² in April across the year — September's 4.25 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.3Bright
24.3Bright
34.3Bright
44.3Bright
54.3Bright
64.3Bright
74.2Bright
84.2Bright
94.2Bright
104.2Bright
114.2Bright
124.2Bright
134.2Bright
144.2Bright
154.2Bright
164.2Bright
174.2Bright
184.2Bright
194.2Bright
204.2Bright
214.2Bright
224.2Bright
234.2Bright
244.2Bright
254.2Bright
264.2Bright
274.2Bright
284.2Bright
294.2Bright
304.2Bright
Planning a trip in September

Hazard calendar for Vieng Xai

In seasonPeak

In September, Vieng Xai sits inside its monsoon season. The full year is below, with each hazard's peak months called out.

Vieng Xai's monsoon runs May–September, when most of the year's rain falls.

Monsoon
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Vieng Xai?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

4.7
Sightseeing
8th-best month of the year
4.8
Beach & pool
6th-best month of the year

September is a reasonable time to visit Vieng Xai for sightseeing.

What to pack for Vieng Xai in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Vieng Xai sees daytime highs around 27°C and nights near 20°C. Pack light clothes and rain gear. About 20 days see rain.

light clothesrain gear

UV index in Vieng Xai in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Vieng Xai peaks around August 12 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 17 at about 7 (high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecVery highExtremeVery highHighAug 12UV 14Dec 17UV 7
UV index (midday)Level
Jan8Very high
Feb9Very high
Mar10Very high
Apr9Very high
May10Extreme
Jun14Extreme
Jul13Extreme
Aug14Extreme
Sep10Very high
Oct9Very high
Nov8Very high
Dec7High

Air quality in Vieng Xai in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Vieng Xai is worst in April — around 288 µg/m³ PM2.5 (very unhealthy), about 35.5× the cleanest month (August, 8 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0306090120150180210240270JanFebMarAprMayJunJulAugSepOctNovDecModerateUnhealthyVery unhealthyUnhealthyGoodModerateApr 15263 µg/m³Aug 128 µg/m³
PM2.5 (µg/m³)Level
Jan20Moderate
Feb28Moderate
Mar98Unhealthy
Apr288Very unhealthy
May64Unhealthy
Jun14Moderate
Jul9Good
Aug8Good
Sep11Good
Oct15Moderate
Nov15Moderate
Dec19Moderate
Location & terrain

Where is Vieng Xai?

Vieng Xai sits at 20.4°N, 104.2°E, 0 m above sea level, in Laos. The nearest listed city is Xam Nua, 19 km away.

Bản Na HỷSơn LaHòa BìnhÍt OngThị Trấn Thuận ChâuThị Trấn Lam SơnNghĩa Lộ

Topography around Vieng Xai

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Vieng Xai.

Within 3 km, the terrain around Vieng Xai has large variations in elevation — a maximum elevation change of 661 m around an average of 915 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,259 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,998 m.

The land around Vieng Xai is covered by trees (65%) and grassland (25%) within 3 km, trees (86%) within 16 km, and trees (82%) within 80 km.

3 km
661 m
16 km
1,259 m
80 km
1,998 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Xam Nua 19 km · Bản Na Hỷ 99 km · Sơn La 107 km · Hòa Bình 125 km · Ít Ong 125 km · Thị Trấn Thuận Châu 127 km · Thị Trấn Lam Sơn 135 km · Nghĩa Lộ 136 km

Laos travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type A / B / C / E / F
230 V · 50 Hz
Prices
≈ 23% of US
price level, 2025
GDP per capita
$2,325
2025
Happiness
5.5 / 10
World Happiness, 2025
Safe drinking water
35%
of population, 2024
Road deaths
17.9
per 100k/yr, 2019
Income group
Lower middle
World Bank
English
Low
EF EPI 461
Religion
Buddhist 65%none 31%other/not stated 2%Christian 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Vieng Xai (20.4068°, 104.2238°, elevation 0 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).